PDF(Pubmed)
Abstract：
Integrins link the extracellular environment to the actin cytoskeleton in cell migration and adhesiveness. Rapid coordination between events outside and inside the cell is essential. Single-molecule fluorescence dynamics show that ligand binding to the bent-closed integrin conformation, which predominates on cell surfaces, is followed within milliseconds by two concerted changes, leg extension and headpiece opening, to give the high-affinity integrin conformation. The extended-closed integrin conformation is not an intermediate but can be directly accessed from the extended-open conformation and provides a pathway for ligand dissociation. In contrast to ligand, talin, which links the integrin β-subunit cytoplasmic domain to the actin cytoskeleton, modestly stabilizes but does not induce extension or opening. Integrin activation is thus initiated by outside-in signaling and followed by inside-out signaling. Our results further imply that talin binding is insufficient for inside-out integrin activation and that tensile force transmission through the ligand-integrin-talin-actin cytoskeleton complex is required.
摘要：
整合素在细胞迁移和粘附中将细胞外环境与肌动蛋白细胞骨架联系起来。细胞内外事件之间的快速协调至关重要。单分子荧光动力学表明，配体与弯曲闭合的整合素构象结合，在细胞表面占主导地位，在几毫秒内跟随两个一致的变化，腿延长和头套开口，得到高亲和力整合素构象。延伸封闭的整联蛋白构象不是中间体，但可以从延伸开放的构象直接进入并提供配体解离的途径。与配体相反，塔林,它将整联蛋白β亚基细胞质结构域连接到肌动蛋白细胞骨架，适度稳定，但不诱导延伸或开放。因此，整合素激活是由外向内的信令启动的，然后是内向外的信令。我们的结果进一步暗示，塔林蛋白的结合不足以进行由内而外的整合素激活，并且需要通过配体-整合素-塔林-肌动蛋白细胞骨架复合物的张力传递。
